1. Field of the Invention
The present invention relates to an apparatus for and method of restoring an image, and more particularly, to an apparatus for and method of restoring an image, by which when the focus of an image is blurred, an image can be restored using the characteristic of a lens.
2. Description of the Related Art
In general, when an image of a predetermined object is obtained using an image pickup apparatus, such as a camera module installed in a digital camera or a portable device, the obtained image is blurred due to many factors.
For example, in relation to focus blur in the obtained image, a light ray incident through a lens is refracted by the lens and then, does not converge on one point, but has a diverging distribution. This causes focus blur to occur because an image is not formed at a pixel of an image sensor at which the image should be formed.
Thus, the characteristic of the light incident on a lens having the diverging distribution that does not converge on one point appears to have a shape varying with respect to the wavelength of the light incident on the lens, the distance between the lens and an object, and the position of the lens on which the light is incident.
Accordingly, a method of restoring an image when an image obtained by an image pickup apparatus is blurred due to focus blur has been studied.
For this purpose, a variety of methods, including non-iterative restoration methods, such as a Wiener filter and a constraint least square (CLS) filter, and iterative restoration methods, such as a Richardson-Lucy method, have been attempted.
However, since the above methods assume that the optical characteristic of a lens is constant with respect to space, it is difficult to reflect a variety of factors causing a light ray incident on a lens having a diverging distribution without converging on one point. In other words, since a blurred image is restored assuming that the position at which light is incident on a lens and the distance between the lens and an object are constant, the restoration of a blurred image is limited.
Furthermore, in addition to the above methods, a method of improving an optical characteristic with respect to the distance between a lens and an object by moving a lens has been attempted. However, this requires an additional driving apparatus for adjusting the movement of a lens in a camera module or the like disposed on a camera or a portable device, thereby incurring additional cost, and increasing the size of the camera module in the portable device which is contrary to the increasingly important aspects of smallness and slimness.